Yes Naku is his sounding board. But I wouldn't call it selfish. To him she is just a simple girl who truly seems to understand him. He never would imagine in his wildest dream that Naku is hiding something big from him. To him she is the most honest and innocent person he has come across in this big bad world.. That's the reason the betrayal is going to hurt him the most..And she cannot just reveal her secrets to him becoz she thinks she is does not fit into his world.
True Vaish...he thinks her life is uncomplicated and protected. I suppose her idealistic view of looking at things makes him think so. so when such a person understands him it takes some burden of his shoulders.